Process for the manufacture of a dressing with thinned edges

ABSTRACT

A dressing with thinned edges comprising a support and an adhesive system of reducing thickness in the direction of the periphery and a process of making the dressing. The process includes the formation of an adhesive system consisting of at least two adhesive layers which are: 
     (i) superimposed to form a set of reducing surface areas from the base, joined to the support, to the top, and 
     (ii) arranged in such a way that two adjacent adhesive layers are joined together and have different surface areas, the edges of one of the two adjacent adhesive layers being offset relative to the edges of the other adhesive layer, the adhesive layer forming the base of the adhesive system, which is joined to the support, having a surface area which is (a) identical to that of the support and (b) greater than the surface area of every other layer of the adhesive system.

FIELD OF THE INVENTION

The present invention relates to a process for the manufacture of adressing with thinned edges. It further relates, by way of a novelindustrial product, to the dressing obtained by this process.

PRIOR ART

EP-A-0 264 299 has disclosed a dressing of the type comprising a supportand an adhesive material consisting of a single adhesive layer, in whichthe edges are chamfered so that the external thickness of the dressing,measured at the periphery, does not exceed 1/4 of the thickness of thedressing in its non-thinned part. The essential advantage of such adressing is that of avoiding creep of the constituent mass of thedressing.

To manufacture this dressing, EP-A-0 264 299 proposes chamfering theedges of the dressing under drastic conditions by applying a "pressureof 10 to 40 metric tonnes" and a temperature of 90 to 110° C. for 1 to 3seconds, to the periphery of a pad consisting of the support coveredwith the adhesive layer.

EP-A-0 358 412 has disclosed a dressing with thinned edges which has astepped profile from the base to the top and comprises three distinctassemblies. According to the description (see column 2 line 50 to column3 line 45), the FIGS. (1 and 2) and the reference numbers (reproducedbelow) of EP-A-0 358 412, these assemblies are as follows:

(a) at the base, a first assembly consisting of a nonwoven support(reference 10) covered on its top face with an adhesive layer (reference11);

(b) on top of the first assembly but with smaller dimensions (length andwidth) than the latter, a second assembly consisting of a film(reference 12) which on the one hand is joined by its lower face to thefirst assembly via the adhesive layer (reference 11) of said firstassembly, and which on the other hand is covered with an adhesive layer(reference 16) on its top face; and

(c) at the top and on top of the second assembly but with smallerdimensions (length and width) than the latter, a third assemblyconsisting of a layer of superabsorbent material (reference 18) linedwith a nonwoven (reference 20), said third assembly being joined to thesecond assembly via the adhesive layer (reference 16) of said secondassembly.

At the time of use, the dressing according to EP-A-0 264 299 is attachedto the skin via the exposed zones of the adhesive layers of the firstand second assemblies.

The technical solutions known in the prior art are found to beimpractical. In fact, the solution proposed by EP-A-0 264 299 foravoiding creep involves a drastic treatment as regards the compressionrequired for chamfering, and the solution proposed by EP-A-0 358 412,which is concerned neither with limiting nor with eliminating creep, hasthe disadvantage on the one hand of increasing the thickness of thedressing at its center, and on the other hand of not being adhesive atits top (i.e. on the upper face of the third assembly).

OBJECT OF THE INVENTION

According to the invention, a novel technical solution is now proposedfor avoiding creep of the constituents of the dressing and formitigating the disadvantages of the prior art.

This novel solution uses at least two adhesive layers superimposed toform a reducing construction from the base to the top, called a steppedconstruction, the upper layer of this construction, i.e. the onesituated at the top, being an adhesive layer.

SUBJECT OF THE INVENTION

According to the invention, a process is therefore recommended for thepreparation of a dressing with thinned edges comprising, joined to oneanother, a support and a film-type adhesive system of reducing thicknessin the direction of the periphery, said process comprising the formationof an adhesive system consisting of at least two adhesive layers whichare

(i) superimposed to form a set of reducing surface areas from the base,joined to the support, to the top, and

(ii) arranged in such a way that two adjacent adhesive layers are joinedtogether and have different surface areas, the edges of one of the twosaid adjacent adhesive layers being offset relative to the correspondingedges of the other adhesive layer, the adhesive layer forming the baseof said adhesive system, which is joined to the support, having asurface area which is (a) identical to that of said support and (b)greater than the surface area of every other layer of said adhesivesystem.

The invention further relates to a dressing with thinned edges whereinsaid adhesive system contained therein consists of at least two adhesivelayers which are

(i) superimposed to form a set of reducing surface areas from the base,joined to the support, to the top, and

(ii) arranged in such a way that two adjacent adhesive layers are joinedtogether and have different surface areas, the edges of one of the twosaid adjacent adhesive layers being offset relative to the correspondingedges of the other adhesive layer, the adhesive layer forming the baseof said adhesive system, which is joined to the support, having asurface area which is (a) identical to that of said support and (b)greater than the surface area of every other layer of said adhesivesystem.

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached drawings:

FIG. 1 is a schematic representation, in section, of a dressing withthinned edges according to the invention containing four adhesivelayers;

FIG. 2 is a schematic representation, in section, of a dressing withthinned edges according to the invention containing three adhesivelayers, the exposed zones of which are covered with a peel-offprotective layer; and

FIG. 3 is a schematic representation, in section, of a dressing withthinned edges according to the invention containing two adhesive layersof different types separated from one another by a film.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1, 2 and 3, the dressing 1 according to theinvention is of the type comprising a support 2 and an adhesive system10. The adhesive system 10 consists of at least two adhesive layers(i.e. in particular: two adhesive layers 11, 12 for the dressing of FIG.3; three adhesive layers 11, 12, 13 for the dressing of FIG. 2; and fouradhesive layers 11, 12, 13, 14 for the dressing of FIG. 1). Forpractical purposes, the total number of adhesive layers used will betwo, three or four. In fact, the advantages which might be gained by a"construction" containing more than four adhesive layers would notjustify the resulting increase in production costs. The dressingaccording to the invention will preferably comprise two or threeadhesive layers.

The thickness of the adhesive system 10 decreases in the direction ofthe periphery when measured in a vertical plane passing through thevertical axis of the dressing. According to FIG. 1, this thicknesscorresponds to the sum of the thicknesses of the four layers 11-14 inthe portion closest to the axis of the dressing, then to the sum of thethicknesses of the lower layers 11-13 and 11-12 on moving away from theaxis, and finally to the thickness of the first layer 11 in the portionfurthest away from said axis.

For the sake of convenience, the lower layer 11, which is also calledthe first layer, is in this case the one covering the support 2 [afterthe dressing has been placed on the skin, it will be the one furthestaway (at the center of the dressing) from the skin], and the upper layer12, 13 or 14, which is also called the last layer, is in this case theone situated at the top of the construction of stepped profile of theadhesive system 10 [after the dressing has been placed on the skin, itwill be the one furthest away from the support 2 and closest to theskin].

The adhesive layers are superimposed to form a set of reducing surfaceareas from the base to the top and arranged so that two adjacentadhesive layers 11/12, 12/13 or 13/14 are joined together, the edges ofthe upper adhesive layer 12, 13 or, respectively, 14 being offsetrelative to those of the adjacent lower layer 11, 12 or, respectively,13. In other words, when considering two adjacent adhesive layers, thesurface area of the upper layer is smaller than that of the adjacentlower layer. The construction which results from the superimposition ofsaid adhesive layers gives the adhesive system 10, and hence thedressing 1, a reducing stepped profile from the base (which has thelargest surface area) to the top (which has the smallest surface area).

The first adhesive layer 11 covers the support 2 and has a surface areaidentical to that of said support. The surface areas of the first layer11 and the support 2 are made equal by cutting the composite consistingof said support 2 covered with said first adhesive layer 11.

The support 2 can have any constitution known to those skilled in theart in the field of dressings, especially (i) a polyurethane filmweighing between 15 g/m² and 80 g/m², (ii) a synthetic nonwoven weighingbetween 5 g/m² and 50 g/m², which is made for example of polyamide,polyester, polyethylene or polypropylene fibers, or else (iii) a complex(or composite layer) formed of a nonwoven covered with a polyurethanefilm.

The adhesive layers 11, 12, 13 and 14 each consist of apressure-sensitive adhesive mass (i.e. self-adhesive mass) known in thefield of dressings, which is preferably hypoallergenic. The followingare particularly suitable: acrylic adhesive masses such as the polymersand copolymers obtained from the monomers C₁ -C₄ -alkyl acrylate and C₁-C₄ -alkyl methacrylate, adhesive masses such as the copolymers obtainedfrom the monomers ethylene, propylene and vinyl acetate, and mixtures ofsuch masses. The following are also suitable: adhesive masses consistingon the one hand of mixtures of three-block copolymers [of the typecomprising a single chain unit of three blocks, such aspolystyrene/polyolefin/polystyrene, where the central block (i.e. thepolyolefin fragment) is advantageously totally saturated], plasticizersand, if necessary, at least one tackifier (especially an acrylatematerial because said three-block copolymers are non-adhesive or onlyslightly adhesive), such mixtures being described especially in Frenchpatent application A-2 678 513 (published on 8th Jan. 1993) and thecorresponding foreign patent applications, especially U.S. patentapplication Ser. No. 903 520 (filed on 24th Jun. 1992) and Europeanpatent application A-0 521 761 (published on 7th Jan. 1993), and/or onthe other hand mixtures of synthetic polymers, for examplepolyisobutylenes, with hydrocolloids, for example polyvinyl alcohol,pectin, gelatin or sodium carboxymethylcellulose.

On the one hand the adhesive layers 11 and 12, and on the other hand theadditional layers 13 and 14 when they are present, can be either of thesame type (i.e. they contain the same essential ingredients) or ofdifferent types (i.e. they do not contain the same essentialingredients).

When two adjacent adhesive layers are of different types, it isrecommended to separate them with an interposed film 3 having a surfacearea identical to that of the upper layer, whose edges are offsetrelative to the edges of the larger surface area of the lower layer, asshown in FIG. 3. Such a film 3 can be made of polyethylene,polypropylene or polyurethane, like the support 2.

For practical purposes, if they are present, the additional adhesivelayers 13 and, where appropriate, 14 will be of the same type as thesecond adhesive layer 12 and preferably identical to said second layer12 from the point of view of composition and thickness.

The first adhesive layer 11 and the second adhesive layer 12 will beeither of the same type or of different types, a separating film 3 beingplaced at their interface in the latter case.

Advantageously, each adhesive layer 11, 12, 13 or 14 will have athickness of between 100 and 800 micrometers. Preferably, the firstadhesive layer 11 will have a thickness of 100 to 400 micrometers, thesecond adhesive layer 12 will have a thickness of 100 to 800 micrometerswhen no other adhesive layer is superimposed thereon and a thickness of100 to 400 micrometers when a third layer 13 is superimposed thereon,and, when they are present, the additional layers 13 and, whereappropriate, 14 will have a thickness of 100 to 400 micrometers.

By way of a further preference, on the one hand the film 3 will have athickness of 15 to 20 micrometers when it is made of polyethylene orpolypropylene or a thickness of 15 to 25 micrometers when it is made ofpolyurethane, and on the other hand the support 2 will have a thicknessof 10 to 50 micrometers and preferably 15 to 30 micrometers when it ispresented in the form of a polyethylene, polypropylene or, preferably,polyurethane film.

The stepped profile enables the dressing 1 with thinned edges accordingto the invention to be attached to the skin via the exposed zones 111,112,113 and 114 of the adhesive layers 11, 12, 13 and 14 according toFIG. 1 (or the zones 111, 112 and 113 according to FIG. 2, or else thezones 111 and 112 according to FIG. 3).

Also advantageously, said exposed zones will be covered with a non-stickprotective layer for storage purposes before the dressing with thinnededges according to the invention is used. In other words, the processfor the preparation of the dressing 1 comprises covering the exposedzones with a non-stick protective layer 4, this protective layer beingtemporary and removable by lifting or peeling at the time when saiddressing is placed on the skin.

In a first embodiment of a dressing with thinned edges, it isrecommended to place a first thin adhesive layer 11, consisting of apressure-sensitive and hypoallergenic acrylic mass (copolymer of C₁ -C₄-alkyl acrylate or C₁ -C₄ -alkyl methacrylate) on a support 2 by coatingor transfer, and then to superimpose, by transfer, a second adhesivelayer 12 consisting of a mixture of three-block copolymer (according toFrench patent application A-2 678 513 cited above), plasticizer and, ifnecessary, at least one tackifier, or a mixture of synthetic polymersand hydrocolloids, whose surface area is less than the surface area ofthe first layer in the sense that it is offset relative to the outeredges of said first layer 11 by a distance of between about 0.2 and 1.5cm in particular.

In a first variant of this first embodiment, a flexible film 3, whosesurface area is identical to the surface area of the second adhesivelayer 12, is interposed between the first adhesive layer 11 and saidsecond layer 12 so that the zone 111 of the upper face of the adhesivemass of the first layer 11 is left exposed.

In a second variant of said first embodiment, said second adhesive layer12, which then has a thickness of between 100 and 400 micrometers, iscovered with a third adhesive layer 13. This adhesive layer 13 is of thesame type and thickness as said second layer 12, but has a smallersurface area than said second layer 12, the edges of the third adhesivelayer 13 being offset relative to the outer edges of the second adhesivelayer 12 by a distance of between 0.2 and 1.5 cm in particular.

In a second embodiment of a dressing with thinned edges, it isrecommended to place a first thin adhesive layer 11, having a thicknessof 100 to 400 micrometers, on a support 2 by coating or transfer, andthen to superimpose, by transfer, a second adhesive layer 12 of a typeidentical to that of the first layer 11, having a thickness of between100 and 800 micrometers and a smaller surface area than the first layer,the two adhesive layers 11 and 12 consisting especially of a mixture ofthree-block copolymers, plasticizers and, if necessary, at least onetackifier, or a mixture of synthetic polymers, especially of thepolyisobutylene type, and hydrocolloid compounds, and the edges of thesecond adhesive layer 12 being offset relative to the outer edges ofsaid first layer 11 by a distance of between about 0.2 and 1.5 cm inparticular.

The dressing 1 according to the invention will advantageously beproduced with a simple geometric shape having at least one axis or oneplane of symmetry. In particular, it will be:

inscribed in a truncated pyramid, in which case its base (i.e. theadhesive layer 11 and the support 2) will be polygonal (square orrectangular),

inscribed in a truncated cone, in which case its base will becurvilinear (especially circular, oval or elliptical), or

inscribed in a mixed surface of the truncated pyramid/truncated conetype, in which case its base will comprise at least one rectilinearportion and at least one curvilinear portion.

BEST MODE

The best mode of carrying out the process according to the invention forthe preparation of a dressing with thinned edges containing two adhesivelayers 11 and 12 comprises, from an industrial point of view, threesuccessive steps consisting in:

(1°) placing a first adhesive layer 11 on a support 2 by a solvent-phasecoating technique or a so-called "molten method" technique, depending onthe type of said first adhesive layer 11, and covering said firstadhesive layer 11 with a non-stick temporary support, especially a pieceof siliconized paper;

(2°) placing a second adhesive layer 12 on a final nonstick protectivelayer 4, especially by said so-called "molten method" technique, and, ifnecessary, covering with a flexible film 3 that face of said secondadhesive layer 12 which is not covered with said non-stick protectivelayer 4; and

(3°) forming the dressing by cutting the composite obtained in step (2°)to the requisite dimensions, cutting said non-stick protective layer 4,applying said composite obtained in this way to the composite obtainedin step (1°) after removal of said non-stick temporary support coveringsaid first adhesive layer 11, and then cutting to the requisitedimensions the non-stick protective layer 4, the first adhesive layer 11and the support 2 of the resulting assembly comprising said non-stickprotective layer 4, said second adhesive layer 12, said first adhesivelayer 11 and said support 2.

To prepare a dressing with thinned edges containing more than twoadhesive layers, the procedure is as indicated above (in the best moderelating to a dressing with thinned edges having only the adhesivelayers 11 and 12), on the one hand with the following modification tostep (1°) before application of said non-stick temporary support:

the first adhesive layer 11 is covered with a second adhesive layer 12which has been cut out beforehand and, if appropriate, provided withsaid flexible film 3 on its lower face, and

said second adhesive layer 12 is covered, if appropriate, with a thirdlayer 13 which has been cut out beforehand, and on the other hand with amodification to step (2°) such that it involves only the formation ofthe composite containing the upper adhesive layer 13 or 14, step (3°)then involving the cutting of the composite containing the upperadhesive layer, the application of this composite to that obtained insaid step 1, and then the final cutting.

Other advantages and characteristics of the invention will be understoodmore clearly from the following description of Examples, which in no wayimply a limitation but are given by way of illustration.

EXAMPLE 1

According to the best mode described above, a dressing with thinnededges is prepared which comprises the adhesive layers 11 and 12. Thisdressing contains:

as the support 2, a polyurethane film having a thickness of 30micrometers;

as the first adhesive layer 11, an acrylic mass based on an ethylacrylate/methyl methacrylate/2-hydroxyethyl methacrylate copolymer andhaving a thickness of 250 micrometers;

as the separating film 3, a polyethylene film having a thickness of 15micrometers;

as the second adhesive layer 12, an adhesive mass consisting of amixture of (i) a polystyrene/polyethylene-butylene/polystyrenethree-block copolymer, (ii) petrolatum, (iii) the synthetic resinWINGTACK 95 marketed by GOODYEAR, and (iv) sodium carboxymethylcellulose(CMC) [where the means (i) and (ii), which are not adhesive, are thosedescribed in Example 1 of French patent application A-2 678 513 citedabove, the means (iii) provides said mass with its adhesive property byvirtue of its tackifying power, and the means (iv) provides said masswith its absorbent property]and having a thickness of 450 micrometers;and

as a non-stick protective layer 4, a siliconized film.

EXAMPLE 2

According to the best mode described above, a dressing with thinnededges is prepared which comprises three adhesive layers, namely thelayers 11, 12 and 13. This dressing contains:

as the support 2, a polyurethane film having a thickness of 50micrometers;

as the first adhesive layer 11, an acrylic mass based on an ethylacrylate/methyl methacrylate copolymer and having a thickness of 200micrometers;

as the separating film 3, a polyurethane film having a thickness of 20micrometers;

as the second adhesive layer 12, an adhesive mass consisting of thethree-block copolymer/petrolatum/synthetic resin/CMC mixture describedin Example 1 above and having a thickness of 250 micrometers;

as the third adhesive layer 13, an adhesive mass identical in itscomposition and thickness to that of the second adhesive layer 12 whichit covers; and

as a non-stick protective layer 4, a siliconized film.

EXAMPLE 3

In the manner indicated above for Example 2, a dressing with thinnededges is prepared which comprises three adhesive layers 11, 12 and 13.This dressing is identical to that of Example 2 except that (i) thefirst adhesive layer 11 is an adhesive mass consisting of thethree-block copolymer/petrolatum/synthetic resin/CMC mixture describedin Example 1 above and having a thickness of 400 micrometers, (ii) theadhesive layers 12 and 13, identical to the layers 12 and 13 of Example2, each have a thickness of 300 micrometers, and (iii) the flexible film3 between the adhesive layers 11 and 12 has been omitted.

EXAMPLE 4

In the manner indicated above for Example 2, a dressing with thinnededges is prepared which comprises only two adhesive layers, 11 and 12.The two adhesive layers, which have the same composition, consist of thethree-block copolymer/petrolatum/synthetic resin/CMC mixture, the firstlayer 11 having a thickness of 400 micrometers, the second layer 12having a thickness of 600 micrometers and the two layers 11 and 12 notbeing separated by a flexible film.

What is claimed is:
 1. A process for the preparation of a dressing whichis thinner at the edges than at a central portion comprising a supportand an adhesive system of reducing thickness in the direction of theperiphery, said process comprising the formation of an adhesive systemconsisting of at least two adhesive layers which are(i) superimposed toform a set of reducing surface areas from the base, joined to thesupport, to the top, and (ii) arranged in such a way that two adjacentadhesive layers are joined together and have different surface areas,the edges of one of the two said adjacent adhesive layers being offsetrelative to the edges of the other adhesive layer, the adhesive layerforming the base of said adhesive system, which is joined to thesupport, having a surface area which is (a) identical to that of saidsupport and (b) greater than the surface area of every other layer ofsaid adhesive system.
 2. A process according to claim 1 in which theformation of said adhesive system involves a first adhesive layerforming the base of said adhesive system, and a second adhesive layer,which contains the same essential ingredients as the first adhesivelayer.
 3. A process according to claim 1 in which the formation of saidadhesive system involves a first adhesive layer forming the base of saidadhesive system, and a second adhesive layer which is not the same asthe first adhesive layer.
 4. A process according to claim 2 in which theadditional adhesive layers, which form said adhesive system with thefirst and second adhesive layers, contain of the same essentialingredients as said second adhesive layer.
 5. A process according toclaim 3 in which a flexible film is provided in order to separate saidfirst and second adhesive layers when the latter are of different types,said film not covering the zone of the first adhesive layer which isexposed by the superimposition of the second adhesive layer.
 6. Aprocess according to claim 1 in which all the adhesive layers of saidadhesive system contain the same essential ingredients.
 7. A processaccording to claim 1 wherein the exposed zones of the adhesive layers ofsaid adhesive system (10) are covered with a non-stick protective layer.8. A process according to claim 1 for the preparation of a dressingwhich is thinner at the edges than at a central portion containing twoadhesive layers and, said process comprising three successive stepsconsisting in:(1°) placing a first adhesive layer on a support andcovering said first adhesive layer with a non-stick temporary support;(2°) placing a second adhesive layer on a final non-stick protectivelayer and, if necessary, covering with a flexible film that face of saidsecond adhesive layer which is not covered with said non-stickprotective layer; and (3°) forming the dressing by cutting the compositeobtained in step (2°) to the requisite dimensions, cutting saidnon-stick protective layer, applying said composite obtained in this wayto the composite obtained in step (1°) after removal of said non-sticktemporary support covering said first adhesive layer, and then cuttingto the requisite dimensions the non-stick protective layer, the firstadhesive layer and the support of the resulting assembly comprising saidnon-stick protective layer, said second adhesive layer, said firstadhesive layer and said support.
 9. A dressing which is thinner at theedges than at a central position comprising a support and an adhesivesystem of reducing thickness in the direction of the periphery, whereinsaid adhesive system consists of at least two adhesive layers whichare(i) superimposed to form a set of reducing surface areas from thebase, joined to the support, to the top, and (ii) arranged in such a waythat two adjacent adhesive layers are joined together and have differentsurface areas, the edges of one of the two said adjacent adhesive layersbeing offset relative to the edges of the other adhesive layer, theadhesive layer forming the base of said adhesive system, which is joinedto the support, having a surface area which is (a) identical to that ofsaid support and (b) greater than the surface area of every other layerof said adhesive system.
 10. A process according to claim 3 in which theadditional adhesive layers, which form said adhesive system with thefirst and second adhesive layers, contain the same essential ingredientsas said second adhesive layer.
 11. A process according to claim 1 inwhich said adhesive layers comprise a member of the group consistingof:a) c₁ -c₄ -alkyl acrylate and methacrylate polymers and copolymers;b) ethylene, propylene and vinyl acetate copolymers; c) mixtures ofthree-block copolymers of polystyrene/polyolefin/polystyrene andplasticizers; d) mixtures of synthetic polymers with hydrocolloids; ande) mixtures thereof.
 12. A process according to claim 11 in which saidmixture of three block copolymers of polystyrene/poleolefin/polystyrenecomprises at least one tackifier.
 13. A process according to claim 11 inwhich said synthetic polymer is a polyisobutylene.
 14. A processaccording to claim 11 in which said hydrocolloid is selected from thegroup consisting of polyvinyl alcohol, pectin, gelatin and sodiumcarboxymethylcellulose.
 15. A process according to claim 1 in which onesaid adhesive layer is an ethyl/methyl/methacrylate/2-hydroexyethylmethacrylate copolymer and one said adjacent adhesive layer is a mixtureof a polystyrene/polyethylene-butylene/polystyrene three-blockcopolymer, petrolatum, a tackifier and sodium carboxymethylcellulose.